Advanced Light-Duty Powertrain and Hybrid Analysis (ALPHA) Tool User's Guide for Off-Cycle Credit Evaluation


            Advanced Light-Duty Powertrain and

            Hybrid Analysis (ALPHA) Tool User's

            Guide for Off-Cycle Credit Evaluation
&EPA
United States
Environmental Protection
Agency

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     Advanced Light-Duty Powertrain and
    Hybrid  Analysis (ALPHA) Tool User's
     Guide for Off-Cycle  Credit Evaluation
                     Assessment and Standards Division
                    Office of Transportation and Air Quality
                    U.S. Environmental Protection Agency
      NOTICE

      This technical report does not necessarily represent final EPA decisions or
      positions.  It is intended to present technical analysis of issues using data
      that are currently available. The purpose in the release of such reports is to
      facilitate the exchange of technical information and to inform the public of
      technical developments.
United States
Environmental Protection
Agency
EPA-420-B-12-051
August 2012

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1. Background

       The Advanced Light-Duty Powertrain and Hybrid Analysis (ALPHA) was created by
EPA as an analysis tool to estimate the Greenhouse Gas (GHG) emissions from Light-Duty
(LD) vehicle sources.   It is a physics-based, forward-looking, full vehicle simulator, which is
capable of simulating various vehicle types and powertrain technologies.  The software is a
freely-distributed, desktop computer based application, built on MATLAB/Simulink.

       The version 1.0 of the simulation tool consists only of conventional vehicles and
should only be used for off-cycle technology evaluation, such as effects on GHG by electrical
load reduction technology, road load reduction technology by active aerodynamics, and
engine start-stop technology.  The next version of the tool will include hybrid and electric
vehicles, and can be used for various vehicle technology effectiveness evaluation purposes in
addition to the off-cycle technology evaluation.

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2. Introduction to ALPHA

This section introduces the basics of the vehicle model in ALPHA and provides details
on simulation inputs and parameters as well as the model architecture. First, the simulation
tool is introduced in terms of its scope, capability, and model architecture, and detailed
descriptions on predefined inputs and parameters are provided.

2.1. Vehicle Model

2.1.1. Scope and Capability

As mentioned previously, the ALPHA tool was created for the LD GHG regulatory
analysis purposes. It is capable of simulating a wide range of conventional and advanced
engines, transmissions, and vehicle technologies over various driving cycles. The tool
evaluates technology package effectiveness while taking into account synergy effects among
vehicle components and estimates GHG emissions for various combinations of future
technologies. Therefore, the simulation model is capable of providing reasonably (though
not absolutely) certain predictions of fuel economy and GHG emissions of specific vehicles to
be produced in the future. The model is also capable of simulating power-split and P2
hybrid vehicles as well as non-hybrid vehicles with a Dual-Clutch Transmission (DCT), under
warmed-up conditions. However, the hybrid vehicle simulation models are not included in
this first version of the tool. The application of the ALPHA version 1.0 should only be
limited to evaluating certain off-cycle technologies and their impacts on GHG improvements.
Additional simulation capabilities such as automatic transmissions, cold-start conditions, and
other hybrid architectures including PHEV and electric vehicles are being pursued by EPA for
future use.

2.1.2. Model Architecture

The ALPHA is a full vehicle simulator that uses the same physical principles as
commercially available vehicle simulation tools (such as Autonomie, AVL-CRUISE, GT-
Drive, Ricardo-EASY5, etc.). In order to ensure transparency of the models and free public
access, EPA has developed the tool in the MATLAB/Simulink environment with a completely
open source code of the vehicle model. For the 2017 to 2025 GHG rule, EPA used the
simulation tool in a more limited manner: to quantify the amount of GHG emissions reduced
by improvements in A/C systems and off-cycle technologies, as explained in Chapter 2 of the
Regulatory Impact Analysis (RIA).

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All vehicle models in ALPHA consist of three levels: system level, component level,
and functional level. There are six systems in the model: Ambient, Driver, Electric, Engine,
Transmission, and Vehicle. Some of the systems (e.g. Electric, Engine, Transmission, and
Vehicle) consist of components, each of which represents a physical entity that makes up the
system. Functions are mathematical equations that represent the systems and/or components.
The overall architecture of the vehicle model is summarized in Table 1. Further details on
the model architecture can be found in Chapter 2 of RIA.
System
Ambient
Driver
Electric
Engine
Transmission
Vehicle
Component Models
N/A
N/A
Accessory (electrical)
Accessory (mechanical), Cylinder
Clutch, Gear
Final Drive, Differential, Axle, Tire, Chassis
Table 1. High-Level Architecture of Vehicle Model

2.2. Simulation Inputs and Parameters

Although the vehicle model in ALPHA is flexible in its architecture and formation that
the user can simulate any type of vehicles by defining desired powertain and vehicle inputs,
EPA has decided to pre-define many of the simulation inputs and model parameters in order
to limit the tool's application to the off-cycle technology evaluations. The following
sections describe these pre-defined simulation inputs and model parameters included in the
version 1.0 of ALPHA.

2.2.1. Ambient C ondition

As described in Chapter 2 of RIA, the Ambient system defines surrounding
environment conditions, such as pressure, temperature, and road gradient, where vehicle
operations are simulated. By default, the environmental conditions defined in this system
are in accordance with the standard SAE practices - air temperature of 25°C, air pressure of
101.325 kPa, and air density based on the Ideal Gas law which results in a density of 1.20
kg/m3. The road gradient is set to 0 %, indicating a vehicle moving on a flat surface.

2.2.2. Electric System

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For the purpose of evaluating A/C as well as off-cycle technologies, the APLHA has
modeled the electrical system as a constant power consumption devise as a function of the
vehicle category. It basically represents the power loss associated with the starter, alternator,
and other electrical accessories. This type of simplification was made since the purpose of
the tool was A-B comparisons only, i.e. relative difference between case A and case B on
GHG emissions.
As the base load from electrical components, EPA assumed 153 W for all vehicle
types. For simulating the A/C load, on the other hand, EPA adopted the power curves of
A/C compressors with displace of 210 cc, published by an A/C equipment supplier, Delphi.
Also, in an effort to characterize an average A/C compressor load in the presence of widely
varying environmental conditions in the United States, EPA adopted data from the National
Renewable Energy Laboratory (NREL) to estimate environmental conditions associated with
typical vehicle A/C usage. In order to associate each vehicle type with appropriate A/C
compressor size, EPA scaled the curve based on the displacement volume ratio. For
determining indirect A/C impact on fuel consumption increase for various vehicle types, EPA
estimated A/C compressor sizes of 120 cc, 140 cc, 160 cc, and 190 cc for small, medium,
large passenger cars, and light-duty pick-up truck, respectively. By taking into account these
compressor sizes relative to 210 cc, EPA created A/C load curves for the four vehicle types,
as shown in Figure 1. As for the A/C fan load, EPA assumed 250 W for all vehicle types.
More details on the A/C compressor modeling can be found in Chapter 2 of RIA.
A/C Load Demand

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2.2.3. Engine and Transmission

The types of engines and the corresponding torque and fuel maps are pre-defined by
EPA. Similarly, the transmission parameters such as number of gears, gear ratios, and
shifting schedules are pre-determined and stored as inputs in ALPHA. There are two types
of engines defined in the simulation tool: Baseline Engine and EGR Boost Engine. On the
other hand, there is only one transmission type modeled in the tool: Dual-Clutch Transmission
(DCT). Table 2 shows these parameters defined in the engine and transmission systems.
Vehicle Type
Engine Displacement
Volume (L)
Engine Idle/Redline
Speed (RPM)
Engine Inertia
(kg-m2)
Transmission Gear
Number
Transmission Gear
Ratio
Transmission Gear
Efficiency
Transmission Inertia
(kg-m2)
Small-Size Car
1.5
770 / 6500
0.075
6-speed
4.148, 2.370,
1.556, 1.155,
0.859, 0.686
0.912, 0.927,
0.925, 0.923,
0.917, 0.910
0.204
Medium-Size Car
2.4
680/6000
0.12
8-speed
4.700, 3.130,
2.100, 1.670,
1.290, 1.000,
0.840, 0.670
0.930, 0.940,
0.947, 0.948,
0.946, 0.943,
0.940, 0.935
0.204
Large-Size Car
3.5
600 / 6400
0.175
8-speed
4.700, 3.130,
2.100, 1.670,
1.290, 1.000,
0.840, 0.670
0.930, 0.940,
0.947, 0.948,
0.946, 0.943,
0.940, 0.935
0.204
Pick-Up Truck
5.4
575 / 5000
0.25
8-speed
4.700, 3.130,
2.100, 1.670,
1.290, 1.000,
0.840, 0.670
0.930, 0.940,
0.947, 0.948,
0.946, 0.943,
0.940, 0.935
0.204
Table 2. Engine and Transmission Input Parameters
2.2.4. Driveline and Vehicle

Similar to other systems mentioned previously, the simulation parameters defining
driveline and vehicle are also pre-determined by EPA. It is important to note again that this
type of simplification was made since the purpose of the tool was A-B comparisons only, i.e.
relative difference between a case without an off-cycle technology and a case with an off-
cycle technology on GHG emissions. Table 3 shows these parameters defined in the vehicle
system. It should be noted that the road-load in ALPHA can be represented by either Cd/Cn
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or ABC coast-down coefficients. It is up to the user which road-load model is used for
desired vehicle simulation and analysis.
Vehicle Type
Final Drive Ratio
Axle/Tire Inertia
(kg-m2)
Tire Rolling
Resistance, Crr
Tire Radius (m)
Vehicle Weight (Ib)
Vehicle Frontal
Area (m2)
Aerodynamic Drag
Coefficient, Cd
Coast-Down
Coefficient, A (N)
Coast-Down
Coefficient, B (N/(m/s))
Coast-Down
Coefficient, C (N/(m/s)2)
Small-Size Car
4.24
0.56
0.00774
0.282
2625
2.29
0.29
90.3768
0
0.4000
Medium-Size Car
3.39
0.90
0.01060
0.320
3625
2.30
0.30
170.9230
0
0.4154
Large-Size Car
2.87
0.97
0.01717
0.342
4000
2.40
0.33
305.5040
0
0.4768
Pick-Up Truck
3.73
1.00
0.02074
0.382
6000
3.27
0.41
553.5369
0
0.8072
Table 3. Driveline and Vehicle Input Parameters
2.2.5. Driving Cycles

The ALPHA is designed to simulate five driving cycles: FTP, Highway, US06, LA92,
and SC03. The FTP (Federal Test Procedure) cycle in ALPHA basically represents the
UDDS (Urban Dynamometer Driving Schedule) cycle, which simulates in-city driving
conditions. The Highway driving cycle represents highway driving conditions under 60 mph
whereas the US06 cycle is a high acceleration, aggressive driving schedule, going over well
over 60 mph. The LA92 cycle is often called the Unified driving schedule, and was
developed as an emission inventory improvement tool. Compared to the FTP, the LA92 has
a higher top speed, a higher average speed, less idle time, fewer stops per mile, and a higher
maximum rate of acceleration. Finally, the SC03 cycle is a supplemental driving cycle
designed to test air conditioning systems. These driving cycles are shown Figure 2 to Figure
6, respectively.
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EPA Urban Dynamometer Driving Schedule
Length 1Se>9 seconds - Distance s 7.45 miles - Average Speed s 19.59 mph
60 ••

I50-' J~*\
6 I i
- 40 - - • I
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ft :1 !; .;-";• •:—v
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"3 20 --if i jf i I !!! 1 ! I i j'l (I KHt ? ' M" I 13 I' 1
0 - --
lj*ji O ITji Q
Timt,
Figure 2. FTP Driving Cycle
EPA Highway Fuel Economy Test Driving Schedule
Length ?6S seconds ~ Distance = 10.26 miles"- ^verafe Speed = 48.^ mph
60 T ,». .*»
SO-- ^ _,,-A_^ ___ _ _j.j / '"°Ws/ l/^
40 - - / V V V i (
SO • • I 1
i 20 • I
Test Time, sees
80 -•
I™"
, 60 - •
$ 50 -•
w 40 - • Hi
* | 1
S 30 ' - I I
| 20 - -1 |
10 ••! |
Figure 3. Highway Driving Cycle
US08 or Supplemental FTP Driving Schedule
Simple Period = 596 seconds - Distance = 8.01 miles - Average Speed = 48.37
Test Time, sees
Figure 4. US06 Driving Cycle
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LA92 "Unified" Dynamometer Driving Schedule
Sample Period = 1435 seconds ™ Distance = 9.82 miles - Averaqe Speed = 24.61 mph
70 -
60 ••
1=0-
«l
1 40 ••

I"0"
J 20 -•
£
Q ITS o irj o ir> o it* o tft o moifjoirjo
e
O ITS O ID O ^3 O
Test Time^ sees
Figure 5. LA92 Driving Cycle
SC03 - Speed Correction Driving Schedule
Simple Period 59S seconds * Disiinoe = 3.58 milts - Average Speed » 21.55
90-
,8 20 - -
*,.-.
0 -
o
Test Time, sees
Figure 6. SC03 Driving Cycle
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3. Instruction for Simulation Run

This section describes the user instructions for how to install and use the ALPHA tool.
The general instructions are first given, and then specific examples are provided along with
simulation results.

3.1. ALPHA Installation

3.1.1. Computing System Requirement

There are certain computational requirements that a user should have in order to install
and use ALPHA properly. A computing system used for running the tool needs to have at
least 1 GB of RAM and 1 GB of free disk space. It should have a window-based operating
system with R201 Ib MATLAB applications installed. It must have a minimum of
MATLAB version 7.13, Simulink version 7.8, and Stateflow version 7.8. It also must have
Microsoft Office Excel 2007 or later, which is required to write and read simulation output
files.

3.1.2. File Structure

The user can download the tool package stored in a zip file (ALPHA_vlp0.zip) from
an EPA website, http://www.epa.gov/otaq/climate/alpha.htm. After unzipping in a desired
folder location, the user should see one figure file 'ALPHA_offcyc_gui.fig' which represents
the Graphical User Interface (GUI), one Simulink file 'ALPHA_vlp0.mdl' which is the
vehicle model, and several p-codes which define all necessary model parameters as well as
control the entire simulation process. In the folder, the user should also see two subfolders,
namely 'drive_cycles' and 'param_files'. The folder 'drive_cycles' consists of mat-files,
which represent the five specific driving cycles: FTP, Highway, US06, LA92, and SC03. On
the other hand, the folder 'param_files" contains p-codes which define all model parameters
for ambient condition, driver response, electrical load, engine maps, transmission shifting
schedules, and vehicle-related information.

3.2. ALPHA Run

3.2.1. General Instruction

In order to launch the ALPHA tool and run vehicle simulations, the user must follow
the steps described in detail below.
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3.2.1.1. GUI Launch
• Launch MATLAB and change the working directory to the folder where the ALPHA
files are located.
• In the MATLAB command window, run the p-code 'ALPHA_offcyc_sim' by typing the
name and hitting the 'Enter' key.
• After running the p-code, the command window displays the following message as
shown in Figure 7, and the GUI appears as shown in Figure 8.
Command Window
(J) New to MATLAB? Watch this Video, see Demos, or read Getting Started.
Light-Duty Vehicle Simulation for Off-Cycle Credit #
* 2017-2025 Light-Duty Vehicle Greenhouse Gas Rules *
US Environmental Protection Agency
Office of Transportation and Air Quality
Assessment and Standards Division

* Program Task *
[1] User's Vehicle Parameter Input
- Define vehicle parameters in GUI Window
»
Figure 7. Command Window Display
'*• n ? x
Advanced Light-Duty Powertrain and Hybrid Analysis
(ALPHA) Tool for Off-Cycle Technology Evaluation
Simulation Type—
Single Simulation
Multiple Simulation
Figure 8. Initial Display of ALPHA GUI
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3.2.1.2. Simulation Setup
• The user can select either the 'Single Simulation' option or the 'Multiple Simulation'
option. Upon the selection, the GUI provides a full display of the simulation options
as shown in Figure 9.
- The 'Single Simulation' runs a pair of simulations, one without any off-cycle
technology and another one with a desired off-cycle technology. This
simulation option only lets the user run the simulation for one vehicle type, one
engine type, and one driving cycle with or without the A/C on.
- The 'Multiple Simulation' runs several pairs of simulations, each pair consisting of
one simulation without any off-cycle technology and another one with a desired
off-cycle technology. This simulation option lets the user run a batch of vehicle
simulations for any vehicle types, any engine types, and any driving cycles with or
without the A/Con.
I ALPHA uereion 1.0
Advanced Light-Duty Powertrain and Hybrid Analysis
(ALPHA) Tool for Off-Cycle Technology Evaluation
Simulation Type—
a Single Simulation
Multiple Simulation
Driving Cycle-
FTP

Highway

; US06
LA92

; SC03
Vehicle Type-
Small-Size Car
~] | Default ] Frontal Ares [m2] Default ] Tire Rolling Resistance. Crr ["^Default

O Large-Size Car
^hn;ie v','.?ia,'it [Ibj | Default ] Frontal Area [m2] ] Default ] Tire Rolling Resistance Crr ] Default

With Off-Cycle Technology
Active Aerodynamics. Cd

,'de Technology |
.".Cycle Technology [

Active Aerodynamics. ABC
With.: .nnology |
With Off-Cycle Technology ^^
Start-Stop
Figure 9. Full Display of ALPHA GUI

The user can select a vehicle type, an engine type, and a driving cycle for the 'Single
Simulation' case whereas the user may select more than one choice in each of the
categories for the 'Multiple Simulation' case.
- For vehicle type, there are currently four vehicle types represented in the current
version of ALPHA: small-size car, mid-size car, large-size car, and pick-up truck.
10
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Details of these vehicle types were discussed in Chapter 2 of this documentation.
The next version of ALPHA will include more vehicle types.
- For engine type, there are currently two engine types represented in the current
version of ALPHA: baseline engine and EGR boost engine. Details of these
engine types were discussed in Chapter 2 of this documentation. The next
version of ALPHA will include more advanced engine types.
- For driving cycle, there are currently five driving cycles considered in the current
version of ALPHA: FTP, Highway, US06, LA92, and SC03. Details of these driving
cycles were discussed in Chapter 2 of this documentation. The next version of
ALPHA may include additional driving cycles.
• For each vehicle type, the user can enter desired vehicle parameters such as vehicle
weight [Ib], frontal area [m2], and tire rolling resistance (Crr). If these parameter
values are not entered, then default values are used for simulation. These default
values were provided in Chapter 2 of this documentation. Even if the word 'Default'
is deleted and the spaces are left blank, the default vehicle weight, frontal area, or
tire rolling resistance values will still be used during simulation.
• For the air condition (A/C), however, the user can simulate only one case of either
A/C on or A/C off for both 'Single Simulation' and 'Multiple Simulation' cases.

3.2.1.3. Off-Cycle Technology Input
• ALPHA is designed to evaluate three off-cycle technologies: a technology that
reduces electrical load to the engine, a technology that improves vehicle
aerodynamics, and a technology that turns off the engine during vehicle stops.
• For the 'Multiple Simulation' mode as well as the 'Single Simulation', only one off-
cycle technology can be selected for analysis via vehicle simulation. If none of the
off-cycle technologies is selected, an error message will appear as shown below.
Your off-cycle technology input is not recognized. Please select
off-cycle technology and run your simulation.
• In order to evaluate the effect of the electrical load reduction technology, the user
must select the 'Electrical Load' in the off-cycle technology panel of the GUI. After a
selection is made, then the user must enter desired values of the electrical load in
Wattage.
11
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The value of electrical load with the off-cycle technology must be smaller than
one without it. Otherwise, an error message will appear as shown below.
The electrical load with off-cycle technology must be less than the
electrical load without off-cycle technology. Please enter proper values
for electrical load and run your simulation.
OK
In order to evaluate the effect of the vehicle aerodynamic reduction technology, the
user must select only one of the options, 'Active Aerodynamics, Cd' or 'Active
Aerodynamics, ABC, in the off-cycle technology panel of the GUI. After a selection
is made, the user must enter desired values of the appropriate aerodynamic
coefficients.
- When the 'Active Aerodynamics, Cd' option is selected, the value of Cd with the
off-cycle technology must be smaller than one without it. Otherwise, an error
message will appear as shown below.
| Input Error
The value of Cd with off-cycle technology must be less than the value of
Cd without off-cycle technology. Please enter proper values for Cd and
run your simulation.
When the 'Active Aerodynamics, ABC option is selected, the value of C with the
off-cycle technology must be smaller than one without it. Otherwise, an error
message will appear as shown below. It is recommended that the values of A
and B are kept the same in order to evaluate effects of aerodynamics only.
The value of C with off-cycle technology must be less than the value of C
without off-cycle technology. Please enter proper values for C and run
your simulation.
12
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3.2.1.4. Simulation Run
• After all selections are made and proper inputs are given in terms of 'Simulation
Type', 'Driving Cycle', 'Vehicle Type, 'Engine Type', 'Air Condition', and 'Off-Cycle
Technology', the user must click 'RUN' button in order to start the simulation.
• After the simulation is completed, the tool provides the simulation results by:
- Displaying fuel economy and GHG emissions in the MATLAB command window,
- Displaying plots of the vehicle speed trace following the desired driving cycle(s),
- Creating an output file in excel format and saving it in the same directory where
the ALPHA files are located. A message appears as shown below, indicating an
output file has been created after simulation runs.
Simulation Results
The simulation output has been saved in
"ALPHA simout 2012 0810 104928. xlsx".
3.2.2. Example Run

In this section, two examples of simulation runs are provided, one for 'Single
Simulation' and the other one for 'Multiple Simulation'. The step-by-step procedures of
setting up and executing the simulations are described, and examples of the simulation
outputs are provided.

3.2.2.1. Single Simulation
• Run ALPHA by typing 'ALPHA_offcyc_sim' in the MATLAB command window and
hitting the 'Enter' key. The GUI appears as shown in Figure 8.
• In the 'Simulation Type' panel, select the 'Single Simulation'. Then, the GUI displays
the full simulation options as shown in Figure 9.
• Select desired simulation options in 'Driving Cycle', 'Vehicle Type', 'Engine Type', and
'Air Condition'. For 'Vehicle Type', the user may enter desired vehicle weight,
frontal area, and tire rolling resistance other than the default values.
- In this example, FTP Cycle, Mid-Size Car (with 3500 Ib of vehicle weight, 2.4 m2 of
frontal area, and 0.01050 of tire rolling resistance), Baseline Engine, and A/C Off
are selected.
• Select desired off-cycle technology to evaluate. Enter proper values for the selected
off-cycle technology.
13
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- In this example, the 'Active Aerodynamics, Cd' option is selected. For this
option, 0.30 of Cd without off-cycle technology and 0.28 of Cd with off-cycle
technology are used.
With the above selections for simulation setup and off-cycle technology inputs, the
GUI appears as shown in Figure 10.
Click 'RUN' button to run the simulation. After completing the simulation, the tool
generates the following results.
- In the command window, the fuel economy and GHG emission results are
displayed as shown in Figure 11.
- The simulated vehicle speed traces are plotted with comparisons to the selected
driving cycle as shown in Figure 12.
- An output file is created in Microsoft excel format. The name of the output file
shows exactly when the file was created following a naming convention of
'ALPHA_simout_yyyy_mmdd_hhmmss.xlsx', where yyyy indicates the year, mm
indicates the month, dd indicates the day, hh indicates the hour, mm indicates
the minute, and ss indicates the second when the file was created by the ALPHA
tool. An example of the output file in excel format is shown in Figure 13. The
output file provides the simulation inputs as well as the outputs.
ALPHA version 1.0
Advanced Light-Duty Powertrain and Hybrid Analysis
(ALPHA) Tool for Off-Cycle Technology Evaluation
Simulation Type—
o Single Simulation
Multiple Simulation
Driving Cycle-
t> FTP

Highway
US06

LA92
; SC03
-Vehicle Type-
Small-Size Car
fight [lb| | Default | Frontal Area [m2] | Default ] Tire Rolling Resistance. Crr [ Default [
a Mid-Size Car
Vehicle Weight [Ib] 3500 Frontal Area [m2] 2.4 Tire Rolling Resistance. Crr | 0.01050

Large-Size Car
Vehicle Weight [Id] | Default ] Frontal Ares [m2] | Default Tire Rolling Resistance. Crr Default

O Pick-Up Truck
"I Default Frontal Ares [m2] | Default ] Tire Rolling Resistance. Crr f~Default
Off-Cycle Technology—
Electrical Load [W]
Without Off-Cycle Technology
With Off-Cycle Technology
a Active Aerodynamics. Cd
Without Off-Cycle Technology 0.30
With Off-Cycle Technology 0.28

Active Aerodynamics. ABC
. ut Off-Cycle Technology |
With Off-Cycle Technology ^^^^
-Engine Type-
o Baseline Engine
; • Start-Stop
Figure 10. Example GUI for Single Simulation
14
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Light-Duty Vehicle Simulation for Off-Cycle Credit
2017-2025 Light-Duty Vehicle Greenhouse *
"OS Environmental Protection agency
Office of Transportation Air Quality
Assessment and Standards Division

Program- Task *
[1] User's Vehicle Parameter Input
- Define vehicle parameters in SOI Window
[21 LD Vehicle Simulation
- simulations for user-defined driving cyclefsj
[3J Result Display
- Display simulation results on MPS l

Simulation Result without Off-Cycle Technology *
» Mid-Size Car, FTP Cycle, Baseline Engine
Percent fine by = 0.85 %
Fuel Economy = 26.54
GBG Emission = 331.07 g/mile

Simulation Result with Off-Cycle Technology *
» Mid-Size Car, FTP Cycle, Baseline Engine
Percent Time Missed by = 0.85 %
Fuel Economy = 26.97
GHG Emission = 329.55 g/nile
END OF
Figure 11. Example of Single Simulation Output in Command Window
FTP Cycle Simulation without Off-Cycle Technology
FTP Cycle Simulation with Off-Cycle Technology
so

40
30
20
10
"c

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200 400 600 800
Time (sec)

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.•|..,i....i.-.. .•!.
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d Speed
Speed

* •
1000 1200 14

40
Q_
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03
20
10
00 C

....v.. •
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AS
'

200

s ;j' "

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400

! i 1 i 1
; Actual Speed
:• ; : -

.....'l.......... .:..........„;.„.........:...........
• J4 i ; _

i :

| -I'i''- '''* V"' ;^'!. fi ;':: '. ••'
-)-} H- •-; j[.;|..j.5/....4...j.J....j.;.-
|i| ! !;!| ; Hi :||
600 800 1000 1200 14
Tme (sec)
Figure 12. Example of Vehicle Speed Trace Output
15
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mr~
1 I Si mi
1 Icimi
1 Simulation Parameters
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3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
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19
20
21
22
23
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Simulation Type
Vehicle Type
Vehicle Weight [Ib]
Vehicle Frontal Area [m2]
Tire Rolling Resistance, Crr
Driving Cycle
Engine Type
Air Condition

Off-Cycle Technology (OCT)
> Active Aerodynamics
Cd without OCT
Cd with OCT

Simulation
Fuel Economy without OCT [mpg]
Fuel Economy with OCT [mpg]
GHG Emission without OCT [g/mi]
GHG Emission with OCT [g/mi]
Single
Medium Car
3500
2.40
0.01050
FTP
Baseline
Off

0.30
0.2S

26.84
26.97
331.07
329.55

Figure 13. Example of Single Simulation Output File

3.2.2.2. Multiple Simulation
• Run ALPHA by typing 'ALPHA_offcyc_sim' in the MATLAB command window and
hitting the 'Enter key'. The GUI appears as shown in Figure 8.
• In the 'Simulation Type' panel, select the 'Multiple Simulation'. Then, a GUI similar
to Figure 9 will appear on the screen.
• Select desired simulation options in 'Driving Cycle', 'Vehicle Type', 'Engine Type', and
'Air Condition'. For 'Vehicle Type', the user may enter desired vehicle weight,
frontal area, and tire rolling resistance other than the default values.
- In this example, all of driving cycles, vehicle types, and engine types are selected
along with the A/C on option.
- For Mid-Size Car, 3500 Ib of vehicle weight, 2.4 m2 of frontal area, and 0.01050 of
tire rolling resistance are used. For Pick-Up Truck, 5800 Ib of vehicle weight, 3.2
m2 of frontal area, and 0.02050 of tire rolling resistance are used. For Small-Size
Car and Large-Size Car, however, the default values are used.
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Select desired off-cycle technology to evaluate. Enter proper values for the selected
off-cycle technology.
- In this example, the 'Electrical Load' option is selected. For this option, 150 W
of electrical load without off-cycle technology and 120 of electrical load with off-
cycle technology are used.
With the above selections for simulation setup and off-cycle technology inputs, the
GUI appears as shown in Figure 14.
Advanced Light-Duty Powertrain and Hybrid Analysis
(ALPHA) Tool for Off-Cycle Technology Evaluation
Simulation Type—
Single Simulation
a Multiple Simulation
Driving Cycle-
a FTP

a Highway
a US06

a LA92
'» SC03
Vehicle Type-
a Small-Size Car
Vehicle Weight [Ib] Default Frontal Area [m2] Default Tire Rolling Resistance, Crr Default

a Mid-Size Car
Vehicle Weight [Ib] 3500 Frontal Area [m2] 2.4 Tire Rolling Resistance, Crr I 0.01050

a Large-Size Car
Vehicle Weight [Ib] Default Frontal Area [m2] Default Tire Rolling Resistance, Crr Default

a Pick-Up Truck
Vehicle Weight [Ib] 5800 Frontal Area [m2] | 3.2 Tire Rolling Resistance, Crr D.02050
-Engine Type
a Electrical Load [W]
Without Off-Cycle Technology 150 ]
With Off-Cycle Technology 120
g ' Active Aerodynamics. Cd
Without Off-Cycle Technology j
With Off-Cycle Technology I
_ ' Active Aerodynamics. ABC
Without Off-Cycle Technology
With Off-Cycle Technology ) [

& Start-Stop
i C
II 1
II 1

Figure 14. Example GUI for Multiple Simulation

• Click 'RUN' button to run the simulation. After completing the simulation, the tool
generates the following results.
- In the MATLAB command window, the fuel economy and GHG emission results
are displayed. A portion of the simulation result display is shown in Figure 15 as
an example.
- The simulated vehicle speed traces are plotted with the scheduled vehicle speed
from the selected driving cycles. Examples of US06 cycles are provided in Figure
16.
- An output file is created in excel format based on the same naming convention as
in the 'Single Simulation' case. A portion of the output file is shown in Figure
17asan example.
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Light-Duty Vehicle Simulation fox Off-Cycle Credit
* 2017-2025 Light-Itaey Vehicle *
US Environmental Protection
Office of Transportation and, Six Quality
Standards Division

* Program *
fl] User's Vehicle Parameter
- Define vehicle paraaeters in GUI
f2] LD Vehicle Simulation
- simulations for user-defined driving cycle(s)
13] Display
— Disdsv siiYulsticn results en MPS 5 C~HG

* Simulation Result without Off-Cycle Tecr.r.clcgy *
» Sir,all-3ize Car, FTP Cycle, Baseline Sr.cir.e
Percent Tirr.e Missed by 2!r.pl" = 1.51 %
Fuel Zcor.cir.y = 31.23 ir.cg
= 284.60

* Simulation with Off-Cycle Technology *
» Small-Size Car, FTP Cycle, Baseline
Percent fey = 1.80%
Fael = 31.34
= 283.55

^" Sirr.'jtls cicrj Resu_t without Off—Cycle 3ecrir.c_ocy *
» Kid-Size Car, FTE Cycle, Baselir.e Sr.cine
Fercsnt Tiir.e Missed by 2rr.p:~. = 1.26 %
* Simulation Result with Off-Cycle Technology *'
» Mid-Size Car, FTP Cycle,
fey = 1.24 %
Fael = 23.Si
= 371.34

* Sinalation Result without Off—Cycle Technology *
» Large-Size Car, FTP Cycle,
by = 2.39 %
Pael Economy = 19.42
= 157.67

* Simulation Result with Off-Cycle Technology *
» Large—Size Car, FTP Cycle, Baseline Engine
Percent Missed by = 2.36 %
Figure 15. Example of Multiple Simulation Output in Command Window
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US06 Cycle Simulation without Off-Cycle Technology
US06 Cycle Simulation with Off-Cycle Technology
100 200 300 400
Time (sec)
500
100 200 300 400
Time (sec)
500
BO
Figure 16. Example of Vehicle Speed Trace Output
1
2
3
4
5
6
7
A
Simulation Parameters
Simulation Type
Vehicle Type
Venicle Weight [Ic]
Vehicle Frontal Are.3 im2]
Tire Rolling Resistance, Crr
Driving Cycle
& Engine Type
9
Air Condition
B
C

Multi 1
Small Car
Default
Default
Default
FTP
Baseline
On
Multi 2
Medium Car
3500
2.40
0.01050
FTP
Baseline
On
D
Multi 3
Large Car
Default
Default
Default
FTP
Baseline
On
E
Multi 4
Truck
5800
3.20
0.02050
FTP
Baseline
On
F
Multi 5
Small Car
Default
Default
Default
Highway
Baseline
On
S
Multi 6
Medium Car
3500
2.40
0.01050
Highway
Baseline
On
H
Multi 7
Large Car
Default
Default
Default
Highway
Baseline
On
1 J K
Multi S
Truck
5SOO
3.20
0.02050
Highway
Baseline
On
Multi 9
Small Car
Default
Default
Default
US06
Baseline
On
Multi 10
Medium Car
3500
2.40
0.01050
US06
Baseline
On
L
Multi 11
Large Car
Default
Default
Default
US06
Baseline
On
M
Multi 12
Truck
5800
3.20
0.02050
US06
Baseline
On
11
12
13
14
15
16
"
is
19
20
21

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Off-Cycle Technology (OCT)
» Electrical Load Reduction
Load without OCT (W)
Load with OCT [W]

Simulation Outputs
-, :„,.-.,,,,...,„,<,;,,

GHG Emission with OCT Lg/mi]

150.0
120.0

31.23
31.34
284.60
283.55

150.0
120.0

23.83
23.89
372.93
371.94

150.0
120.0

19.42
19.44
457.67
457.04

150.0
120.0

13.76
13.77
646.05
645.21

150.0
120.0

45.53
45.62
195.19
194.82

150.0
120.0

38.86
38.92
228.68
228.32

150.0
120.0

29.56
29.60
300.61
300.26

150.0
120.0

19.86
19.87
447.53
447.16

150.0
120.0

27.32
27.38
325.27
324.57

150.0
120.0

23.30
23.32
381.37
381.08

150.0
120.0

19.15
19.19
464.05
463.09

150.0
120.0

12.95
12.96
686.06
685.79
Figure 17. Example of Multiple Simulation Output File
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